This invention relates generally to shaft joints and particularly to the boot seals of such joints used to exclude contaminants from entering the joint housing in service.
Joints for torque-transmitting shafts, such as those mounted at the ends of a prop shaft of a motor vehicle typically include a joint housing having an open end that receives a stub end of the prop shaft. The end is closed by a boot seal fixed to the housing with a neck that surrounds and seals against the shaft for excluding contaminants such as dust, dirt, water, salt, road grime, and the like from entering the housing during service in order to protect the internal working components of the joint for damage.
In cases where the joint is to be pre-lubricated with grease and shipped elsewhere for assembly with the shaft, measures must be taken to contain the grease within the housing and to exclude contaminants from entering the housing during shipping. A common approach to protecting the joint during shipment has been to install a removable shipping plug into the open unoccupied neck of the seal. The shipping plug has a cylindrical shank corresponding in dimension to the stub end of the shaft which is inserted into the open neck. An enlarged head on the trailing end of the plug confronts the end of the neck to limit insertion and to help seal the opening. The shank is interior to a housing and comes into contact with the grease.
Once the joint arrives at its destination and is ready for assembly with the shaft, the shipping plug is removed. As the shank of the plug is withdrawn from the boot seal, it has a tendency to carry some of the grease along with it, causing unwanted grease to accumulate on the neck portion of the boot seal. The presence of such grease on the neck region is undesirable, as it can allow the neck portion to move axially along the shaft and/or twist on the shaft in service, impairing the sealing effectiveness of the boot seal. Accordingly, there is a need in the industry for a joint seal that is not prone to the accumulation of such grease on the neck region upon removal of the shipping plug to ensure superior performance of the seal in service.
A joint assembly according to the invention mountable on a rotatable torque-transmitting shaft comprises a joint housing have an open end, a boot seal fixed to the housing for sealing the open end having a neck portion with a generally cylindrical inner wall defining a passage terminating at a free open end of the neck portion for receiving a stub end of the shaft therein, and a shipping plug removably disposed within the passage for temporarily closing the passage prior to mounting the joint assembly on the shaft in order to contain grease within the housing and to exclude contaminants from entering the housing through the neck portion.
According to the invention, an annular wiper rib is provided on the inner wall of the neck portion in wiping engagement with the shipping plug. The wiper rib is operative to scrape grease from the shipping plug upon its removal from the neck portion thereby preventing the grease from passing into the neck portion beyond the wiper rib.
One advantage of the present invention is that the same plug configuration and installation/removal techniques can be used as before, while the subject wiper rib feature operates to remove the grease from the plug during its removal to keep the grease from contaminating the neck portion.